The primary objective of the proposed project is to determine the biochemical, morphological and physiological mechanisms controlling the excitation-effector coupling of the bioluminescent systems in coelenterates, especially the hydroid Obelia and the pennatulid Renilla. It is expected that these studies will serve to eludicate the mechanisms underlying other excitation-effector systems such as the action of muscle. The biochemical studies will seek 1) to determine the relationship between the calcium activated photoproteins and their associated green fluorescent proteins (which acts as the final photon emitter), and 2) to establish whether or not the photoprotein is a stable intermediate in a luciferin-luciferase reaction. Standard biochemical methods will be used. The physiological and morphological experiments will seek to establish 1) the electro-chemical mechanisms involved in the junctional coupling between the excitation system and the photocyte effector, 2) the function and structure of the photoprotein-green fluorescent protein complex of the subcellular particles within the photocytes, and 3) the type of relationship that this complex has to membrane depolarizations and calcium fluxes which probably occur to cause ultimate photon emission. Intracellular recording, electron and fluorescence microscopy, and image intensification will be employed.